Prime Minister Stephen Harper sought to shore up Conservative support among older voters by promising a new tax break for single and widowed seniors if his government is re-elected.

The $2,000 tax credit would translate into up to $300 a year in reduced income tax for nearly 1.6 million single seniors who have private pension income beyond CPP and OAP.

Eligible seniors could combine it with the existing $2,000 pension income tax credit for a combined benefit of up to $600 a year.

“It is an affordable commitment,” Harper said Tuesday in North Vancouver, noting it will be phased in over four years at an eventual annual cost of nearly $400 million. “It helps the seniors who need it most.”

Both the NDP and Liberals have promised to increase the Guaranteed Income Supplement for lower income seniors.

The Liberals say their proposed immediate 10 per cent hike to GIS payments would add up to an extra $920 a year for a low-income senior.

The Conservatives have sought to portray Liberal and NDP promises as unaffordable and therefore unreliable.

The Liberals and NDP have also pledged to scrap the Conservatives’ 2012 decision to make many future seniors wait an extra two years until age 67 before becoming eligible for OAP and GIS. That change is to be phased in starting in 2023.

Both Opposition parties aim to expand CPP, drawing criticism from Harper that their approaches amount to hefty payroll tax hikes.

The NDP and Liberals both would unwind another Harper government change they say benefits only the wealthy – the increased $10,000 contribution limit for Tax Free Savings Accounts.

But both parties say they would preserve income splitting for seniors.

Earlier in the week, NDP leader Tom Mulcair pledged to bolster health care transfers to the provinces with an extra $1.8 billion.